Download SMIC Biology

Name:
# ___ Team Learning (SY12-13)
DNA Replication, Transcription, and Translation
Introduction:
Two primary scientific achievements of the 20th century were the discoveries that DNA (deoxyribonucleic acid) is the
genetic material of the cell, and that this macromolecule is organized in the form of a double helix. Subsequent research by
numerous scientists has led us to understand how DNA is replicated prior to cell division and how it controls cell metabolism.
The goal of this workshop is to master the basics of three processes: DNA replication, the synthesis of RNA (ribonucleic
acid) by transcription, and the building of proteins through translation. These three processes are bound by a universal genetic
code that is common to most living things.
Prepare for your workshop by reading assignments in the textbook, reviewing your lecture notes, and participating in
group discussions.
This lesson requires some students to volunteer as team leaders. Leaders should facilitate discussion, keep the group on
task, and check team members’ homework when needed. Team leaders need to meet with the teacher briefly outside of class time
to prepare for the next day’s lesson. At the end of the workshop, team leaders will be evaluated by their team and by their teacher,
which determine the amount of extra credit received.
Part 1. Vocabulary Building. Complete the chart below.
Describe its structure Briefly explain its
Vocabulary
or explain what it is
function
State its
location
What is its relationship to one or
more other terms on the list?
DNA
Nucleotide
Complementary
base pairs
Ribose sugar
Codons
the genetic code
Anticodons
rRNA
Peptide bond
Proteins
Based on Peer-Led Team Learning: Introductory Biology, Module 7 by Joseph G. Griswold – Progressions, v.7, No.1, Fall 2005
Page 1 of 6
Part 2. Molecules and Symbols. Draw your solutions to each of the problems in this section using the following symbols:
Problem
Solution
1. A single DNA nucleotide with a
guanine base
2. A single strand of DNA with the
base sequence ATCG
3. A polypeptide with the sequence:
Alanine (Ala), serine (Ser), tyrosine
(tyr) – Substitute the abbreviation for
“X” in the oval
4. A strand of mRNA with the base
sequence UACG
5. A DNA template with the
sequence ACGT attached to the
complementary mRNA strand
Based on Peer-Led Team Learning: Introductory Biology, Module 7 by Joseph G. Griswold – Progressions, v.7, No.1, Fall 2005
Page 2 of 6
6. A double strand of DNA. One
strand has the base sequence
TTAG.
7. A codon of mRNA with the base
sequence GCU with the anticodon of
tRNA attached as it would be in
translation.
Part 3. Transcription of RNA from DNA
The diagram below illustrates the transcription of mRNA from DNA.
1. Where does this process take place?
2. Fill in the base sequence on the unlabeled DNA strand that acted as a template for making the mRNA. Write small!
3. Fill in the base sequence for the newly synthesized strand of mRNA. Write small!
4. Label the mRNA strand and the DNA template.
5. Circle the codons on the mRNA strand. How many codons are on the mRNA strand?
Based on Peer-Led Team Learning: Introductory Biology, Module 7 by Joseph G. Griswold – Progressions, v.7, No.1, Fall 2005
Page 3 of 6
RNA Editing Occurs Between Transcription and Translation
The initial strand (pre-mRNA) that was just produced contains some nucleotide sequences that code for (carry instructions
for) proteins and some that don’t. The sequences that code for proteins are called exons (they will be expressed). The sequences
that do not code for any proteins are called introns (they are found in-between the expressed sequences). Specific enzymes cut
out the introns and paste together the exons to create an mRNA strand that only contains exons. In eukaryotic cells, an enzyme
adds additional (specific) nucleotides as a cap and a tail for the final mRNA molecule. Only then does the mRNA leave the nucleus.
See page 365 for a diagram.
Part 4. Translation: Synthesis of Proteins
The figure below illustrates part of the process of translation.
1. Label the figure with the following terms: mRNA, ribosome (contains rRNA), tRNA, polypeptide chain, codon, anticodon, free
amino acids
2. Where could this process take place? (2 possible locations)
3. What will be the final product of this process? (3 possible names)
Part 5: Review
Meet in your peer-led groups to discuss the answers above. Take turns leading the discussion within your group to resolve
answers to questions. When time is up, peer leaders should bring up any items their groups were unable to resolve.
Part 6: Scholarly Definitions
Team leader: Divide the work amongst the group, including yourself. Your team should evaluate the definitions that follow by
circling any parts that are incorrect and correcting the definition. Write TRUE if the entire definition is already correct. Be prepared
to share your work with the group.
1. DNA: located in the nucleus; a polymer made of amino acids; contains ribose, phosphate groups, and nitrogen bases;
replicates during the S phase of the cell cycle; one strand acts as a template for mRNA replication; strands can be divided into 3base sequences called codons.
2. mRNA: m stands for "messenger"; is synthesized in the nucleus; the process of synthesis is called translation; works in
polysaccharide synthesis on ribosomes in the cytoplasm; is composed of 3-base units called codons; is single stranded; has T
substituted for U when it is synthesized from DNA.
Based on Peer-Led Team Learning: Introductory Biology, Module 7 by Joseph G. Griswold – Progressions, v.7, No.1, Fall 2005
Page 4 of 6
3. template: a name given to a DNA strand that serves in mRNA synthesis; has a sequence of triplets which determine the
codons of mRNA; works by binding complementary nucleotides which are then linked to form the mRNA strand; binding to free
nucleotides is by hydrogen bonding.
4. codons: an example would be ATC; many occur in sequence on mRNA molecules; sites of attachment for the anticodons
of tRNA; determine the order in which amino acids attach to form a polypeptide; are complementary to DNA triplets from which they
were formed initially.
5. tRNA: are short polynucleotide strands; t stands for "target"; carries a sugar at one end for polysaccharide synthesis; at
the other end of the molecule is an anticodon for attachment to codons of mRNA; if the mRNA codon were AUG, the anticodon of
tRNA would be UAC; occurs in many varieties to carry different amino acids.
6. transcription: manufacture of proteins using mRNA and tRNA; occurs on ribosomes in the rough endoplasmic reticulum;
involves the encoding of a sequence of triplets into a complementary sequence of codons.
7. translation: the raw materials for the process are free amino acids in the cytoplasm or rough ER; requires enzymes to
attach amino acids to one another; occurs on free ribosomes or ribosomes of the rough endoplasmic reticulum; mRNA and tRNA
each play an important role; final product is a polypeptide.
8. DNA replication: a double DNA strand separates into two single strands; each single strand attracts complementary
nucleotides which attach by hydrogen bonding; an enzyme hooks adjacent nucleotides together forming the new double strand;
occurs before a cell divides in mitosis.
9. nucleotides: are the monomers from which DNA and RNA are synthesized; occur in four different varieties in DNA, and
three varieties in RNA; each one includes a sugar, nitrogen base and a phosphate group; are synthesized into RNA and DNA in
the nucleus; occur only in the nucleus.
10. ribosome: some of its parts are manufactured in the nucleus; consists of rRNA and proteins; serves as a location for
protein synthesis; has two connected parts (subunits), one large and one small; occurs free in the cytoplasm and attached to the
walls of the rough endoplasmic reticulum.
Based on Peer-Led Team Learning: Introductory Biology, Module 7 by Joseph G. Griswold – Progressions, v.7, No.1, Fall 2005
Page 5 of 6
Part 7: Short Problems
Team leader: Divide the work amongst the group, including yourself. Following the problem solving period, each student will
present the solution to the rest of the team.
1. A newly formed complementary strand of DNA has the base sequence AGGTCTGAGCCTAGC. What is the sequence of
bases in the template from which it was synthesized?
2. If this new DNA strand were used as a template for mRNA, what is the base sequence of the mRNA strand formed?
How many codons are present in the mRNA strand?
3. Using the genetic code on p. 367 of your text, determine the amino acid sequence of a polypeptide synthesized from mRNA
with the following base sequence: CGUCGCUCUGUGCAUUAA
4. Given a single strand of DNA with the base sequence AGCCATTGCGAAACT, what is the sequence of a complementary DNA
strand?
5. An mRNA strand has the base sequence AUGACCUUAGACCUAGCG. How many codons are present?
sequence of triplets for the DNA strand that acted as a template for its synthesis?
What is the
6. What is the amino acid sequence that would be produced by the mRNA strand in question 5?
7. Given a DNA template of TACGGAACTTTCGTCCGA, what is its complementary mRNA strand?
8. Determine the anticodons for the tRNAs that attach to the mRNA strand CGUCGCUCUGUGCAUUAA.
9. What is the amino acid sequence that would be produced by the mRNA strand above?
10. A polypeptide has the amino acid sequence: Leucine-Alanine-Aspartate-Glycine-Valine-Glutamine
Determine the sequence of codons in the mRNA molecule that would code for this polypeptide by using the genetic code on
the last page of this handout. If there is more than one possible codon, use the first one listed in the genetic code.
Figure out the DNA base sequence for the molecule above.
Based on Peer-Led Team Learning: Introductory Biology, Module 7 by Joseph G. Griswold – Progressions, v.7, No.1, Fall 2005
Page 6 of 6